History of the Peloponnesian War
Thucydides
Thucydides. History of the Peloponnesian War. Crawley, Richard, translator. London and Toronto: J. M. Dent and Sons Ltd.; New York: E. P. Dutton and Co., 1914.
regarding him who assists them then as a friend, even if thus far he has been a foe, and him who opposes them then as a foe, even if he has thus far been a friend; indeed they allow their real interests to suffer from their absorbing preoccupation in the struggle.
Weigh well these considerations, and let your youth learn what they are from their elders, and let them determine to do unto us as we have done unto you. And let them not acknowledge the justice of what we say, but dispute its wisdom in the contingency of war.
Not only is the straightest path generally speaking the wisest; but the coming of the war which the Corcyraeans have used as a bugbear to persuade you to do wrong, is still uncertain, and it is not worth while to be carried away by it into gaining the instant and declared enmity of Corinth. It were, rather, wise to try and counteract the unfavorable impression which your conduct to Megara has created.
For kindness opportunely shown has a greater power of removing old grievances than the facts of the case may warrant.
And do not be seduced by the prospect of a great naval alliance. Abstinence from all injustice to other first-rate powers is a greater tower of strength, than anything that can be gained by the sacrifice of permanent tranquillity for an apparent temporary advantage.